Enhancement of low-temperature activity of γ-Fe2O3-modified V2O5-MoO3/ TiO2 catalysts for selective catalytic reduction of NOx with NH3

In this study, a series of gamma-Fe2O3-modified V2O5-MoO3/TiO2 (VMT) catalysts was prepared by wet impregnation method. The gamma-Fe2O3-modified catalysts exhibited excellent catalytic performance, and 1.25 wt% gamma-Fe2O3 content improved the deNOx efficiency at 150 degrees C from 54% (unmodified VMT catalyst) to 84% (modified catalyst). BET, XRD, XPS, NH3-TPD, H2-TPR, and in situ DRIFTs were employed to characterize the physicochemical properties and reaction mechanisms of the catalysts. The introduction of gamma-Fe2O3 increased the V5+/V4+ ratio, surface chemisorbed oxygen content, redox ability, and a number of acid sites in the prepared catalysts. XPS confirmed the addition of gamma-Fe2O3 introduced new charge transfer pathways (Fe3+/Fe2+ <-> V5+/V4+). In situ DRIFTs suggested that the addition of gamma-Fe2O3 to the catalyst significantly increased the adsorption capacity of catalyst for NH3 and NOx, while also exerting a strong activating effect on the adsorbed NH3. Furthermore, selective catalytic reduction over the VMT and 5PEG@1.25Fe-VMT catalysts followed the Eley-Rideal (E-R) mechanism. At temperatures above 200 degrees C, the 5PEG@1.25Fe-VMT catalyst also followed the Langmuir-Hinshelwood (L-H) mechanism.